In this Pre-Release 4 mojang patches the following that will be available when 

Minecraft 1.2 is Released THIS IS JUST THE PRE-RELEASE.


-------------------------------------------------------------------------------------



1. Many minor bug fixes and tweaks

2. Doors have been changed to properly detect if they are open or closed. 

3. Double doors in existing maps will need to be updated

4. Villagers will move indoors during night and rain, and socialize with each other

5. Zombies will break down wooden doors on hard difficulty

6. Added cat sounds

7. Better movement for mobs in water

8. Added rare mob item drops


-----------------------------------------------------------------------------------

INSTALL INTRUCTIONS 


Windows- 

1. Type %appdata% in the search bar 

2. .minecraft/bin

3. change your current .jar file to whatever you like ( Example: minecraft1.1.jar )

4. now just change the current .jar file that you downloaded to minecraft.jar

-----------------------------------------------------------------------------------


MAC - 

1. goto Finder/User/Library/Application Support/minecraft 

2. FOLLOW STEPS 2-4 above.